The invention relates to a velocity probe for measuring the velocity of a fluid stream, and particularly for measuring the change in flow patterns of a fluid stream. Prior art devices have had several problems associated therewith. Many prior art devices in the general field of the invention, such as that shown in U.S. Pat. No. 3,759,098, require at least two sets of orifices within members disposed within a flow stream, or within the flow stream confining member itself. This may require extra expense and the necessity of forming a plurality of orifices (which should be sealed) within structural members, affecting the transferability of a measuring device from one system to another. Also, many prior art devices, U.S. Pat. No. 1,834,392 for example, have a tendency to clog up when placed in the flow stream if the fluid has impurities and contaminants therein.
According to the teachings of the present invention, the above problems are avoided. A velocity probe is provided that has only a single connection to a chamber confining a fluid stream to be sensed. The probe has an opening in a sensing portion thereof that is orientated in a particular manner so that the probe opening will not clog up during normal use in a contaminated fluid stream, yet will effectively sense the velocity of the stream.
The velocity probe of the present invention is especially useful in sensing the flow reversal occurring in the boundary layer of material flowing through a compressor and thereby controlling impending surge conditions in a compressor, as more fully described in the abovementioned parent application Ser. No. 408,809. The probe of the present invention is adapted to be inserted into the boundary layer of material flowing through a compressor, and will not clog up as a result of the contaminated flow often associated with a compressor.